MRI systems, especially high field cavity magnet MRI systems, have always been widely accepted due to their high imaging quality and comprehensive functionalities. However, due to the structural characteristics of the magnet in a high field MRI system, the imaging zone is an enclosed cavity, causing some patients to feel a strong sense of confinement, which affects its clinical application. In order to increase the comfort of the patient lying in the closed magnet cavity, a ventilation system is usually installed to provide fresh air to the patient.
At present, the ventilation system for the MRI system often features a motor driven fan, as shown in FIG. 1, a structural diagram of an MRI system and its ventilation system according to the prior art. In FIG. 1, the MRI system consists of a cavity magnet (10), a gradient coil (20) close to the cavity magnet (10) and an enclosure (30), with an air outlet (40) in the enclosure close to the upper side of the patient's head. The ventilation system consists of a motor (50), a centrifugal fan (60) and an air duct (70), wherein the motor (50) drives the centrifugal fan (60), and sends airflow to the air outlet (40) of the MRI system through the air duct (70). However, because the motor (50) contains many magnetic components which can severely affect the evenness of the magnetic field of the MRI system's magnet (10), this can only be installed far from the cavity center of the magnet (10), as shown in FIG. 1. This lengthens the air duct (70) from the ventilation system to the air outlet (40) of the magnet cavity, thus leading to greater ventilation resistance, attenuated air volume and lower ventilation efficiency.
In addition, the system is complicated in terms of structure and more expensive in terms of cost due to severe electromagnetic interference from the running motor upon the MRI system, which requires the design of a special shielding device, and also due to the need of the motor for a special power supply such as an AC transformer and a rectifier, which are very large in size, and furthermore, the need for a special shielding device with consideration to electromagnetic compatibility with the magnet.